On 1/10/24 15:44, Martin KaFai Lau wrote:
On 1/10/24 2:17 PM, thinker.li@xxxxxxxxx wrote:
The proposed solution here is to add PTR_MAYBE_NULL annotations to
arguments
[ ... ]
== Future Work ==
We require an improved method for annotating arguments. Initially, we
anticipated annotating arguments by appending a suffix to argument names,
such as arg1__maybe_null. However, this approach does not function for
function pointers due to compiler limitations. Nevertheless, it does work
for functions. To resolve this, we need compiler support to enable the
inclusion of argument names in the DWARF for function pointer types.
After reading the high level of the patch,
while it needs compiler work to support decl tagging (or arg name) in a
struct_ops's func_proto, changing the info->reg_type of a struct_ops's
argument have been doable in the ".is_valid_access" without new kernel
code change in verifier/btf.c.
btf_ctx_access() mentioned in the original message is a help function
called by the implementation of .is_valid_access. So, just like you
said, they definitely can be handled by .is_valid_access it-self.
Do you prefer to let developers to handle it by themself instead of
handling by the helpers?
Take a look at the bpf_tcp_ca_is_valid_access() which promotes the
info->btf_id to "struct tcp_sock". The same could be done for
info->reg_type (e.g. adding PTR_MAYBE_NULL).
